In recent years, printed circuit boards have been used extensively in electrical equipment. For example, computers are routinely constructed of a plurality of printed circuit boards each containing a portion of the electronics required to allow the computer to operate. In computer designs it is common to require several circuit boards to be inserted in a closely-spaced parallel relationship into a card cage having a card guide for every circuit board. A contact arrangement consisting of a card edge or connector on the leading edge of each of the circuit boards engage an electrical connector when the circuit board is fully inserted into the card cage.
The amount of force required to seat a circuit board into a backplane is dependant on the number of contacts and type of electrical connectors used. Typically, the more contacts that must be mated, the more force that must be used to seat the circuit board. Today, computer circuit boards utilize a high number of electrical connections which require high insertion force. Therefore a large amount of force is required to properly seat circuit boards into their backplane connectors. The task of seating the boards is made even more difficult because of the close spacing of circuit boards in the card cage.
With respect to extraction of a circuit board from the backplane, tight board-to-board spacing presents an obstacle to firmly grasping the trailing edge of the circuit board. Also it takes a large amount of force to extract a circuit board utilizing high insertion force connectors. This force is hard to apply in the typically small space available for grasping with a human hand.
It is common to provide a cam lever, pivotally attached to a trailing edge corner of a circuit board to facilitate circuit board removal. The camming action of such a device against the card cage provides a limited amount of extraction, and the device often does not aid in circuit board insertion.
The prior art devices require separate engaging devices to be mounted onto the card guides. These engagement devices complicate and increase the time and expense required for the card cage to be assembled.
Prior art extraction systems also require tools and fixtures to attach them onto the circuit boards. Typically, screws or rivets are used to attach the cam lever to the circuit board. To allow the lever to pivot as required, the screw or rivet holding the lever to the circuit board can not be too tight. However, if the lever is not restrained sufficiently, then the lever will not properly engage the card guide and will not extract the circuit board properly--if at all. Therefore special tools and fixtures are used to assure the proper retention of the lever to the circuit board which increases the time and expense required to assemble a complete circuit board assembly. Additionally, the lever attachment step typically requires a separate "station" on the manufacturing line. This station must be designed into the assembly line and the power for the tools has to be provided. Each additional station adds to the space required in assembly and increases the fixed and variable overhead costs which must be recovered by the product sales price.
What is needed in the industry is a circuit card inserter and extractor device which can be assembled onto a circuit board quickly and without tools and can supply the high insertion and extraction forces required by high insertion force connectors used today.